Various processes have been developed to apply coatings to glass containers for different purposes, including decoration, adhesion and glass strengthening for damage prevention. For example, U.S. Pat. No. 3,522,075 discloses a process for coating a glass container in which the container is formed, coated with a layer of metal oxide such as tin oxide, cooled through a lehr, and then coated with an organopolysiloxane resin-based material over the metal oxide layer. In another example, U.S. Pat. No. 4,099,486 discloses a process for electrostatically coating a glass container, which is electrically conductive so that a charge differential can be created by grounding the container. The process includes supporting a container in an inverted position on a non-conductive chuck, and contacting a ground pin with a neck finish of the container or longitudinally extending the ground pin into the interior of the container and into contact with an inside bottom of the container to complete a ground path. The process also includes heating the container to the range of 150-400 degrees Fahrenheit to reduce surface resistivity, and increase conductivity, of the container, and then spraying the container with charged particles, which are attracted to the conductive grounded surface of the container.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to provide a glass container with an electrically conductive surface, which may allow the container to be electrostatically coated without the need to use grounding pins, to heat containers to increase surface conductivity, and/or to apply an additional conductive coating layer.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A method of coating a glass container in accordance with one aspect of the disclosure includes the steps of (a) contacting an exterior surface of the container with a mixed gas including a metal compound and a dopant compound including at least one dopant selected from the group consisting of F, Cl, B, P, and Sb, to form a doped metal oxide coating on the exterior surface of the container to reduce electrical resistivity of the exterior surface of the container, and (b) electrostatically applying an organic coating to the exterior surface of the container after step (a). According to a preferred aspect of this method, the organic coating may be applied at an ambient temperature, without having to use grounding pins, without having to heat the container, and without having to apply an additional conductive coating layer after depositing the hot end coating.
In accordance with a further aspect of the disclosure, there is provided a glass container that includes a closed base at one axial end of the container, a body extending axially from the closed base and being circumferentially closed, and an open mouth at another axial end of the container opposite of the base. An exterior surface of the container includes an organic coating electrostatically applied over an electrically conductive hot end coating that includes a metal oxide and a dopant selected from the group consisting of: F, Cl, B, P, and Sb.
In accordance with another aspect of the disclosure, there is provided a method of manufacturing a glass container including the steps of forming the container, applying a hot end coating to an exterior surface of the container, wherein the hot end coating includes a metal oxide, and a dopant to reduce electrical resistivity of the exterior surface of the container. The method also includes annealing the container, applying a cold end coating to the exterior surface of the container, inspecting the container, and electrostatically depositing an organic coating on the container without having to use grounding pins, without having to heat the container, and without having to apply an additional conductive coating layer after applying the hot end coating.